The present invention relates to a process for enhancing the properties of caramel colorants, and more particularly, to a process for the color enrichment and desalting of caramel colorant utilizing centrifugal size exclusion chromatography.
Caramel colorant is a coloring agent widely used in food, pharmaceutical and beverage manufacturing industries, most particularly in the manufacture of cola-type soft drinks. The caramel colorant is used to impart the amber shade extensively found in carbonated beverages, pharmaceutical and flavoring extracts, candies, soups, bakery products and numerous other foods. Caramel colorant is made commercially by heating a solution of sugar with or without the addition of a catalyst in a process known as caramelization. Heating the solution during caramelization causes several complex chemical reactions such as polymerization, rearrangement and condensation to occur. In currently used caramelization processes, the extent of heating is limited because if the heating treatment is too extensive, additional reactions occur which impart undesirable characteristics to the caramel colorant product such as charring, unmanageable viscosities, diminished solubility and instability which may lead to the tendency for the colorant to resinify on storage. Commercial caramel colorant, which has not been refined beyond the conventional caramelization and having a minimum of undesirable properties, contains color-imparting solids accounting for less than one-half of the total solids contained in the product, the remainder of the solids being materials not contributing directly to the coloring power of the mixture. Attempts have been made to determine the various constituents in caramel colorant by a variety of means but the constituents revealed in preliminary tests have indicated the complexity of the product and have often dissuaded further investigations. These attempts have revealed however that the color-imparting solids of the colorant are of relatively high molecular weight whereas the remainder of the materials which do not impart color are of relatively low molecular weight.
The coloring power, or tinctorial power, of caramel colorant is the basis on which it is marketed commercially. The higher the coloring power, the more attractive the product is to the user. The amber shade produced by caramel colorant has become so fixed in the consumer's acceptance of certain foods and beverages that when these products have low or lighter color intensity, it often causes the food or beverage to be viewed as being inferior or lacking in strength. Therefore, it becomes a necessity for manufacturers of commercial caramel colorant to have economical processes for supplying colorant of high coloring power. Thus, the need for efficient and practical processes for the enhancement of caramel colorant is present in the caramel colorant, food and beverage industries.
Over the years, many diverse processes have been developed to enhance the coloring power of caramel colorant solutions and to remove undesirable, non-color contributing contaminants from the caramel solutions. Examples of known processes for producing caramel colorants of increased coloring power include separation of a colorant solids concentrate by the addition of coagulating or precipitating agents, e.g. ethanol, to the caramel colorant solutions; separation of a colorant solids concentrate from caramel colorant previously treated with microorganisms, and dialysis of caramel colorant to obtain a colorant solids concentrate. A more recent example of a caramel colorant concentrating process is the use of ultrafiltration such as the process disclosed in U.S. Pat. No. 3,249,444 to Bollenback et al.
It was reported by Stinson and Willits, Journ. Assoc. Offic. Anal. Chem. 46(2), pp. 329-330 (1963), that acid-proof caramel colorant could be separated from ash salts and sucrose by subjecting the caramel colorant to gel filtration using cross-linked dextran as the filter gel. According to the report, it was possible to separate acid-proof type caramel colorant from ash salts and sucrose in one pass through a large static column of Sephadex type filter gel.
While the above-mentioned processes for the enhancement of caramel colorant have been generally satisfactory in terms of the product produced, the processes have not been entirely satisfactory for implementation in commercial operations of large capacity due to, among other things, the relatively long periods of time necessary to affect an enhancement of the caramel colorant.